It was a sign in an Atlanta bus station in the summer of 1961 that awoke something in a teenage Lucy Buckner.

“I was on a Greyhound bus and they had the ‘colored only’ signs on the water fountains,” she recalled. “Having grown up in Ohio, I kind of wanted to test the water.” A kindly Georgia aunt stopped her before she got into trouble. But something changed in Buckner that day. “That started it,” she said.

Buckner, now a 68-year-old grandmother from Burnsville, will take part in her third civil rights march in Washington on Saturday to mark the 50th anniversary of her first: The 1963 March on Washington for Jobs and Freedom, the forum for Rev. Martin Luther King’s transformative vision of racial justice.

On Friday morning, Buckner boarded the bus at Sabathani Community Center in south Minneapolis, joined by several dozen other marchers, all headed for the Lincoln Memorial, where King galvanized the early civil rights movement with his “I have a Dream” speech.

Much has changed in the last 50 years, Buckner said, while noting that much has stayed the same or even gone backward in the push for equal housing, education and employment. Her life has had its own ups and downs, including a divorce and the raising of three successful daughters. Her oldest, a Maryland police dispatcher, will meet her in Washington.

For Buckner, one constant is the need to keep the nation focused on King’s dream. She marched the first time despite the fears of her father, who grew up in segregated Georgia and who lived just long enough to see Barack Obama become president. Buckner returned to Washington in 1983 for an anniversary march led by King’s widow, Coretta Scott King.

Now, Buckner said, King’s message is as relevant as ever. “Since I’m living,” she said, “I’m going to march in 2013.”

Hattie Bonds, the retired Minneapolis school principal who organized the bus ride from Minneapolis as part of the National Action Network, said Saturday’s march is more than a commemoration of history.

“We’re still struggling with jobs, justice, Dr. King’s dream,” Bonds said. “It’s important for us to say, ‘Look, we have not arrived just because we have an African-American president.’ Let’s stay focused and help our country to grow and get better.”

Bonds points to a sweeping set of metrics in Minnesota that shows the scope of work yet to be done:

• The jobless rate for blacks in Minnesota is triple that of whites, creating one of the largest racial gaps in the nation, even compared to such Deep South as Memphis and Atlanta.

• Fewer than half of blacks in Minnesota graduate from high school, compared to four-fifths of whites.

• Rates of incarceration, free-lunch programs for students and foster care all are disproportionately high for black Minnesotans.

Nationally, the picture is much the same. A Pew Research Center poll released Thursday found that only 26 percent of African-Americans believe the situation for black people has improved in the past five years, while more than one in five say things are worse. That’s in contrast to the 35 percent of whites who believe blacks have made progress in the past five years.

The march organizers recognize that different segments of society will argue about who is to blame or what should be done. This weekend’s gathering in Washington, they said, is intended to serve as a visual reminder that inequality still exists in America.

Bonds sees it not only as an economic fact, but a political one as well.

“The big picture is the total disenfranchisement of certain people in our society,” she said.